1. Field of the Invention
The present invention relates to drilling systems and, more particularly, to a method of and apparatus for producing a combination of vortex and axially disposed erosive jet streams for cleaning, cutting, boring, combinations thereof, and the like.
2. History of the Prior Art
Drill bits for drilling bore holes for oil and/or gas production and the like will typically engage the formation and remove particles therefrom. When drilling the bore holes for well production, there are generally at least two types of formations which a drill bit will encounter: relatively soft shale and hard rock.
When the formation is relatively soft, as with shale, material removed by the drill bit will have a tendency to reconstitute onto the teeth of the drill bit. Build-up of the reconstituted formation on the drill bit is called bit balling and will reduce the depth that the teeth of the drill bit will penetrate the bottom surface of the well bore, thereby reducing the efficiency of the drill bit. Particles of a shale formation also tend to reconstitute back onto the bottom surface of the bore hole. The reconstitution of a formation back onto the bottom surface of the bore hole is called bottom balling. Bottom balling prevents the teeth of a drill bit from engaging virgin formation and spreads the impact of a tooth over a wider area, thereby reducing the efficiency of a drill bit. Higher density drilling muds that are required to maintain well bore stability or well bore pressure control exacerbate bit balling and the bottom balling problems. Therefore, there is a need for drill bits which will reduce drill bit balling and bottom balling that occurs when drilling shale-like formations.
When the formation that the drill bit is engaging is of a harder rock, the teeth of the drill bit press against the formation and densify a small area under the teeth to cause a crack in the formation. When the porosity of the formation is collapsed, or densified, in a hard rock formation below a tooth, nozzles of the conventional drill bits do not have enough hydraulic energy to remove the crushed material below the tooth pit when the tooth is removed. As a result, a cushion, or densification pad, of densified material is left on the bottom surface by the prior art drill bits. If the densification pad is left on the bottom surface, force by a tooth of the drill bit will be distributed over a larger area and reduce the effectiveness of a drill bit. Therefore, there is a need for drill bits that have sufficient hydraulic power to remove the crushed material below a tooth pit in a drill bit when the tooth is removed.